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Converters and Local Oscillators for Flexible Payloads

Objectives

The target of the current contract is the study of new flexible converter for flexible payloads and the fabrication and test of a Prototype EM of the whole unit.

Challenges

A Flexible Converter Demonstrator has been designed, manufactured and tested. The test results confirm that:

1) The concept works, one channel within the complete input frequency range can be moved to any channel within the complete output frequency range.

2) The phase noise cancellation works, the phase noise of the common high frequency LO is cancelled on the output.

Benefits

The converter design is based on the double conversion scheme to overcome the issues of spurious and LO harmonics falling in band. The designed converter is suitable for frequency flexible payloads, where it provides the requested flexibility and re-configurability. The design incorporates European state-of-art large band VCO MMICs.

Features

The general block diagram below shows the Flexible Converter Assembly including the following units: Downconverter, Upconverter, IF Band-pass Filter and Fixed Frequency Oscillator.

performs a frequency conversion of this signal to the selected internal IF band. Bandpass filtering is performed at IF. The downconverted and filtered signal is then upconverted to the applicable downlink frequency by the Upconverter. The amplification according to the requested total gain is distributed to both converters. An LNA can be included in the Downconverter when a receiver function is needed.

The IF filter bandwidth may correspond to the input bandwidth (typically 250 or 500 MHz) in case the complete block of received channels is transferred to the output as a group. The filter may also have a bandwidth corresponding to one channel (typically 36 MHz) in case a channelization of the signal is made at this stage. In this case a set of parallel band-pass filters and parallel Upconverters are used on the payload in correspondence to the number of included channels.

In case of block conversion it is in most cases sufficient to include the synthesizer in the upconverter, the downconverter can use a fixed LO frequency.

The LO signals for the frequency conversion are generated by three

frequency sources. One source is the Fixed Frequency PLO, which

provides a common frequency component for both the Down- and

Upconverter. The other two sources are the frequency synthesizers

located in the Downconverter (if needed) and the Upconverter. These are externally controlled and the frequency is individually selected for each converter.

Plan

An EM demonstrator and a proof of concept is included and finalized in this Project. Next step will be to refine and improve the LO section and continue the design for LO and RF/IF parts towards an EQM model based on a dialog with potential customers.

Current status

The Flexible Payload Converter has been designed up to EM level. The Local Oscillator made by Kongsberg Norspace has been delivered to RUAG and integrated into the EM Demonstrator. A test campaign has been performed on the complete demonstrator and a proof of concept has been successfully performed.

After this proof of concept was made a study of an alternative solution for the Local Oscillator was made. This study has given some valuable inputs on how to improve spurious performance on the complete Local Oscillator and has been one step forward in the development of this Concept.